﻿using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace SQL_Script_Runner
{
	public class Crypto
	{
		private static byte[] _salt = Encoding.ASCII.GetBytes("o6806642kbM7c5");

		/// <summary>
		/// Encrypt the given string using AES.  The string can be decrypted using 
		/// DecryptStringAES().  The sharedSecret parameters must match.
		/// </summary>
		/// <param name="plainText">The text to encrypt.</param>
		/// <param name="sharedSecret">A password used to generate a key for encryption.</param>
		public static string EncryptStringAES(string plainText, string sharedSecret)
		{
			if (string.IsNullOrEmpty(plainText))
				throw new ArgumentNullException("plainText");
			if (string.IsNullOrEmpty(sharedSecret))
				throw new ArgumentNullException("sharedSecret");

			string outStr = null;                       // Encrypted string to return
			RijndaelManaged aesAlg = null;              // RijndaelManaged object used to encrypt the data.

			try
			{
				// generate the key from the shared secret and the salt
				Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

				// Create a RijndaelManaged object
				// with the specified key and IV.
				aesAlg = new RijndaelManaged();
				aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);
				aesAlg.IV = key.GetBytes(aesAlg.BlockSize / 8);

				// Create a decrytor to perform the stream transform.
				ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

				// Create the streams used for encryption.
				using (MemoryStream msEncrypt = new MemoryStream())
				{
					using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
					{
						using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
						{

							//Write all data to the stream.
							swEncrypt.Write(plainText);
						}
					}
					outStr = Convert.ToBase64String(msEncrypt.ToArray());
				}
			}
			finally
			{
				// Clear the RijndaelManaged object.
				if (aesAlg != null)
					aesAlg.Clear();
			}

			// Return the encrypted bytes from the memory stream.
			return outStr;
		}

		/// <summary>
		/// Decrypt the given string.  Assumes the string was encrypted using 
		/// EncryptStringAES(), using an identical sharedSecret.
		/// </summary>
		/// <param name="cipherText">The text to decrypt.</param>
		/// <param name="sharedSecret">A password used to generate a key for decryption.</param>
		public static string DecryptStringAES(string cipherText, string sharedSecret)
		{
			if (string.IsNullOrEmpty(cipherText))
				throw new ArgumentNullException("cipherText");
			if (string.IsNullOrEmpty(sharedSecret))
				throw new ArgumentNullException("sharedSecret");

			// Declare the RijndaelManaged object
			// used to decrypt the data.
			RijndaelManaged aesAlg = null;

			// Declare the string used to hold
			// the decrypted text.
			string plaintext = null;

			try
			{
				// generate the key from the shared secret and the salt
				Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);

				// Create a RijndaelManaged object
				// with the specified key and IV.
				aesAlg = new RijndaelManaged();
				aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);
				aesAlg.IV = key.GetBytes(aesAlg.BlockSize / 8);

				// Create a decrytor to perform the stream transform.
				ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
				// Create the streams used for decryption.                
				byte[] bytes = Convert.FromBase64String(cipherText);
				using (MemoryStream msDecrypt = new MemoryStream(bytes))
				{
					using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
					{
						using (StreamReader srDecrypt = new StreamReader(csDecrypt))

							// Read the decrypted bytes from the decrypting stream
							// and place them in a string.
							plaintext = srDecrypt.ReadToEnd();
					}
				}
			}
			finally
			{
				// Clear the RijndaelManaged object.
				if (aesAlg != null)
					aesAlg.Clear();
			}

			return plaintext;
		}
	}

}